Osteoarthritis of the knee is a major cause of disability in adults and nonsurgical treatments, such as physical therapy (PT), are important interventions for pain care. However, a recent systematic review and data meta-analysis found disappointing results suggesting that few PT approaches are consistently effective for this painful condition.
Shi-Yi Wang, MD — from the Department of Chronic Disease Epidemiology, Yale School of Public Health — and colleagues conducted an extensive literature search for all randomized controlled trials (RCT) examining PT therapies for painful knee osteoarthritis (OA) in community-dwelling adults [Wang et al. 2012]. Eligible interventions included any of those within the scope of PT practice, and comparators included usual care, sham therapy of some sort, or no active treatment.
Writing in the November 6, 2012 edition of Annals of Internal Medicine, the researchers report that, from 4,266 retrieved articles, 193 RCTs published in English and spanning 1970 through February 2012 were selected as qualifying for review. Adequate data were available from 84 RCTs for meta-analyses, providing evidence for 13 PT interventions in terms of their impact on pain, physical function, and disability.
The analyses provided low-strength evidence that aerobic and aquatic exercise improved disability, and that aerobic exercise, strengthening exercises, and ultrasonography (high-frequency sound wave therapy) reduced pain and improved physical function. None of the other individual PT interventions demonstrated sustained benefits on all three of the key efficacy measures. With the exception of wedged shoe inserts, adverse events were uncommon and did not deter participants from continuing any PT treatments.
Overall, the researchers conclude that the strength of evidence was low; although, consistently high adherence to aerobic exercise and strengthening programs appeared to be somewhat advantageous for managing OA knee pain. Wang and colleagues acknowledge that their meta-analyses were hampered by the poor quality of many RCTs and variability in PT interventions and outcome measurements. Future studies should compare combined PT interventions, which is more typical of how PT is generally administered for pain associated with knee OA.
COMMENTARY: A major mission of these Pain-Topics UPDATES articles has been to advocate for more reliable and valid evidence that can foster better pain management. This present study, funded by the U.S. Agency for Healthcare Research and Quality, demonstrates just how difficult that quest may be, given the present state of research in the pain field and the general paucity of high-quality evidence.
Systematic reviews and meta-analyses, themselves, represent the highest level of evidence [as explained most recently in Part 13 here of our “Making Sense of Pain Research” series]. However, in their ambitious review of physical therapies for knee OA, Wang et al. ran into many obstacles.
For one thing, there was a diverse constellation of individual PT interventions to consider. The review included RCTs examining 1) education programs, 2) aerobic exercise, 3) aquatic exercise, 4) strength training, 5) tai chi, 6) therapeutic massage, 7) orthotics (eg, shoe inserts, braces), 8) taping, 9) electrical stimulation, 10) pulsed electromagnetic fields, 11) ultrasonography, 12) diathermy (electrically induced heat), and 13) proprioception exercises (addressing balance, stability, agility). None of these were compared head-to-head with each other or in combination.
Of greatest concern, the researchers acknowledge that clinical trials of individual PT interventions are inconsistent with practice guidelines recommending that a combination of PT modalities should be delivered for treating knee OA. For example, they note that taping or bracing would not be used alone, but in combination with exercise and possibly other PT interventions. So, contrary to the results that Wang et al. discovered, it probably should not be assumed that any of the PT approaches examined could not be of some value as a component of a multimodal approach.
Further confounding of the evidence was possibly due to the fact that most, if not all, patients in the trials examined were taking concomitant pharmacotherapy for pain. It is usually presumed that potential influences of this would be equally distributed across groups in randomized trials and cancel each other out; however, this may not always be the case in small trials. Wang and colleagues note that many of the RCTs in their study did not even include information on other treatments that subjects may have received concurrently during the respective trials.
A few other limitations of this report are worth noting…
- The literature search included only studies published in English and certain databases (eg, Embase) were not searched, so there is a possibility that some RCTs were not discovered. In fact, Wang et al. conceded that there was likely publication bias, without doing formal statistical tests or a sensitivity analysis (eg, Funnel Plot) to assess the extent of this.
- Within each PT modality, most available RCTs were of small size and substantially heterogeneous; that is, they inconsistently measured outcomes or significantly differed from each other in ways that made aggregating their data in a meta-analysis less precise and reliable. The researchers appropriately used random-effects modeling for their meta-analyses; however, they do not provide Forest Plots of the data, so readers cannot more easily assess the extent of this concern for themselves.
- The researchers acknowledge that many trials did not adequately describe the quality and/or intensity of PT interventions or the involvement of therapists, which further impeded a valid data meta-analysis.
- Wang et al. also concede that most RCT reports discussed outcomes as average scores for patients within groups, but did not evaluate how many patients had clinically important or meaningful improvements in pain, function, or quality of life.
In sum, the value of this review and meta-analysis for guiding clinical decision making in recommending specific PT approaches for patients with knee OA is questionable. Unfortunately, more naturalistic studies examining multimodal PT interventions in combination with other therapies (eg, pharmacotherapy), as occurs in everyday practice, pose some formidable obstacles and inherent limitations for producing valid outcomes and strong evidence.
REFERENCE: Wang S-Y, Olson-Kellogg BO, Shamliyan TA, et al. Physical Therapy Interventions for Knee Pain Secondary to Osteoarthritis: A Systematic Review. Ann Intern Med. 2012(Nov 6);157(9):632-644 [article here].
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